DARPA wants a Spec Ops plane with a set of insane characteristics

It can take off vertically with a lead-up (defined as the length of runway needed for take-off) of less than 300 feet, hover in austere environments, and fly forward at more than 450 miles per hour. And, by the way, it’s probably a fixed-wing plane.

That, at least, is the idea behind DARPA’s SPRINT X-plane, a project in the beginning stages of development for use by the U.S. Special Operations Command (SOCOM). The Defense Advanced Research Projects Agency recently called for proposals for a plane with a mind-bending set of capabilities. According to the March solicitation, DARPA wants a scaled demonstrator ready to fly within the next three-and-a-half years.

SPRINT, naturally, stands for “SPeed and Runway INdependent Technologies.”

“The SPRINT Demonstrator Project aims to design, build, certify, and fly an X-Plane to demonstrate the key technologies and integrated concepts that enable a transformational combination of aircraft speed and runway independence for future air mobility platforms,” the solicitation states, adding that the project aims to validate technologies that can be adapted to military aircraft of different sizes.

SPRINT Concept Art. Source (DARPA slide via DefenseOne)

The joint SOCOM-DARPA effort aims to develop an aircraft with the following set of science-bending abilities:

Cruising at speeds equal to or higher than 400 knots true airspeed, or about 460 miles per hour, at elevations between 15,000 and 30,000 feet;
Hovering and stable hover maneuvers;
Transitioning between hover, forward flight, and high-speed forward flight, both forward and back, without losing stability;
Generating and distributing power in all flight modes and during transition between flight modes

The plane should also have a flight radius of at least 200 nautical miles, flight test endurance of at least 90 minutes, and a payload of 5,000 pounds, with a cargo bay large enough to fit a small wheeled vehicle. According to documents, the aircraft will likely weigh between 8,000 and 15,000 pounds unloaded, which is about half the weight of a fighter jet.

A set of MV-22B Osprey tiltrotor aircraft fly in formation above the Pacific Ocean off the coast of Sydney, Australia, June 29, 2017. The MV-22Bs belong to Marine Medium Tiltrotor Squadron 265 (Reinforced). VMM-265 (Rein.) is part of the Aviation Combat Element of the 31st Marine Expeditionary Unit. (Official U.S. Marine Corps photo by Lance Cpl. Amy Phan/Released)

What makes this notional aircraft different from the V-22 tiltrotor Osprey, which can take off like a helicopter and fly like a plane, is velocity: the Osprey reaches top speeds of around 273 knots, or 315 miles per hour, with a slightly lower cruising rate.

DARPA left a lot of mysteries, however, around other specifics, for example, it’s not clear if this future plane would be manned, unmanned, or optionally manned – DARPA’s leaving that up to the companies proposing to build it. And while concept art shows a fixed-wing, streamlined aircraft with windows, it hasn’t excluded the possibility that it will be some kind of rotorcraft or hybrid.

“The need for runway-independent aircraft for combat is growing as publicly available satellite imagery and open-source intelligence communities make it nearly impossible for militaries to hide runways or aircraft,” Technology writer Patrick Tucker wrote at DefenseOne, which published an early report about the project. Runways and airbases are considered particularly vulnerable in a potential near-peer conflict.

Bridging the gap between a helicopter’s freedom of maneuver and an airplane’s speed would indeed be a feat. As Popular Mechanics explained in a 2018 piece, a helicopter’s transition from lift to thrust as it moves forward limits its speed; tellingly, the world’s fastest cars could outrun the Osprey, which remains the world’s fastest rotorcraft.

An AV-8B Harrier with Marine Medium Tiltrotor Squadron (VMM) 163 (Reinforced), 11th Marine Expeditionary Unit (MEU), prepares to land aboard the amphibious assault ship USS Boxer (LHD 4) during an air power demonstration. The Marines and Sailors of the 11th MEU are conducting routine operations as part of the Boxer Amphibious Ready Group in the eastern Pacific Ocean. (U.S. Marine Corps photo by Cpl. Israel Chincio)

The Marine Corps, which needs aircraft that can take off and land on short amphibious ship flight decks, has two fixed-wing jets that can achieve vertical lift and a hover state, the AV-8B Harrier and the F-35B Joint Strike Fighter. Both aircraft have powerful nozzles and lift fans, respectively, that direct exhaust downward to create thrust. It’s a fuel-sucking and noisy process, and sometimes comes with side effects: the F-35B’s lift fans generate enough heat that they’ve actually damaged ship flight decks.

DARPA seems to be looking for something different, namely a plane that can hover at will in austere environments, without needing a special surface to take off and land on, and which can then reach cruising speeds similar to that of a Gulfstream or Learjet. And it wants to get there fast. The first design phase is set to take just six months, and flight tests could occur as early as fiscal 2026.

After DARPA completes testing on a SPRINT demonstrator, it plans to hand the aircraft over to SOCOM for additional trials and inspection.